Erythrasma is a superficial skin infection caused by Corynebacterium minutissimum, and is characterized by sharply demarcated erythema, mostly in the skin folds.
Corynebacterium minutissimum is an aerobic, catalase-positive, non-spore-forming, nonmotile, Gram-positive, diphtheroid bacillus, parasitic in the nose, pharynx, conjunctiva, external auditory canal, and skin surfaces of healthy humans. Under appropriate conditions such as warm and humid skin and skin injuries, the bacteria can invade the stratum corneum, causing infection.
Signs and Symptoms
Skin lesions are sharply demarcated patches with irregular edges. The color of the skin lesions varies with the duration, and initial red is followed by brown or brownish red. The surface may have branny scales. The disease occurs mostly in the groin, armpit, gluteal fold, skin under the breast, and interdigital areas. Subjective symptoms are usually absent, but pruritus and lichenification may occur in the groin and perianal area.
The skin lesions of generalized erythrasma are characterized by sharply demarcated, reddish brown patches widely distributed in the trunk and extremities, predominantly in patients with diabetes and other wasting diseases. Long duration and obvious pruritus are present. It is believed that diabetes may be the precipitating factor of erythrasma.
The bacteria and hyphae can be found on the smears with scales scraped from the skin lesions in Gram stain in microscopy. After 18 - 36 hours of culture in the tissue culture medium containing 20% calf serum and 2% agar, colonies can be seen. The skin lesions reveal coral red fluorescence under a Wood’s lamp examination.
According to the characteristics of skin lesions, occurrence mostly in the skin folds, the bacteria and hyphae found in microscopy, and coral red fluorescence under a Wood’s lamp examination, the disease can be diagnosed.
Topical antifungal cream is effective, and clotrimazole or miconazole cream can be administered for 2 weeks. Patients with large skin lesions can be treated with erythromycin 0.25g orally 4 times a day for 2 weeks. Topical sulfuric ointment, salicylic acid ointment or fucidin cream, or oral tetracycline is effective.
The disease is easy to relapse after healing, and antibacterial soap bath or talcum powder can prevent recurrences.